NHTSA Complaint #10736179 — 2011 BMW X5 DIESEL SAV

I HAVE A 2011 BMW X5 335D WITH A LITTLE OVER 73K MILES. JUST RECENTLY MY CHECK ENGINE LIGHT CAME ON AND AFTER A TRIP TO THE SHOP THE TECHS SAID IT WAS DUE TO A FAULTY DEF (DIESEL EXHAUST FLUID) SENSOR. UNFORTUNATELY THIS PART IS ~$930 AND IS ON A NATIONAL BACK ORDER. I ASKED IF THE PART IS A MANUFACTURE RECALL, BUT IT'S NOT. I'M MIND BOGGLED BECAUSE I HAD THE EGR REPLACED TWICE UNDER MANUFACTURE RECALL FREE OF CHARGE, BUT THIS DEF SENSOR ISN'T. HOW CAN THIS BE?.?.? THIS PART HAS TO DO WITH EMISSIONS STANDARDS AND DUE TO THE PART BEING UNAVAILABLE I'M FORCED TO DRIVE WITH A CHECK ENGINE LIGHT UNTIL THE SHOP IS ABLE TO GET THE PART. WHO KNOWS WHAT FURTHER DAMAGE THIS WILL DO TO THE X5 AND WORST OFF, IF I DON'T GET THIS REPAIRED SOON, I'LL FAIL A SMOG CHECK AND CAN'T DRIVE MY CAR AT ALL. I'M HOPING THE NHTSA OR EPA FOLKS CAN VIEW THIS AS A MANUFACTURE RECALL ISSUE DUE TO A FAULTY PART AND TO MEET EPA STANDARDS....UPDATED 11/13/15 *BF UPDATED 1/4/2016*JS